Process of preparing pure tin compounds.



UNITED sTArEs PATENT OFFICE.

ELMER A. SPERRY, OF BROOKLYN, NEW YORK.

PROCESS OF PREPARING PURE TIN COMPOUNDS.

Specification of Letters Patent.

Patented May 12, 1908.

Applicationfiled April 27, 1907. Serial No. 370,681.

To all whom it may concern:

Be it known that I, ELMER A. SPERRY, a citizen of the United States,residing at Brooklyn, in the'county of Kings and State of New York, haveinvented new and useful Improvements in Processes of Preparing 'Pure TinCompounds, of which the following i is a specification.

My invention relates to the commercial production of compounds of tin ofgreat purity. I These compounds may be either liquid or solid. Amongthese products may .be mentioned the bichlorid of commerce, which is asolution of stannic chlorid; butter of tin"of commerce, which is ahydrated form of stannic chlorid with definite water of crystallization;tin crystalsstannous chlorid; pink salts, tin oxyhydrate; tin oXid, andthe like.

The invention consists in first converting the metallic tin in the tinbearing material into an anhydrous compound preferably one with a haloen base, for instance, anhydrous tetrachloricf, which it is found willnot combine with ordinary foreign materials, as do solutions, especiallystannic solutions. The method of preparation preferably being such thatthe reaction is under temperature control at all times and wherein theforeign bodies and substances contained in the tin bearing material arefound in and commingled with the anhydrous tin compound so pro duced.While in the anhydrous form, the matecial may thus be more easilypurified and freed, for instance, from iron, or other foreign substanceswhichmay be present in the cheaper forms of tin, or tin bearingmaterial: for instance, the anhydrous stannic chlorid may bereadilydistilled or otherwise suitably rendered pure, it being practical torender this substance perfectly pure, thus eliminating entirely theforeign materials in- -'cluding gaseous impurity, such as chlorin wherepresent.

The intermediate product, viz: the anhydrous liquid may be considered asthe base from which the various terminal products are derived by atreatment suitable to each. During the preliminary step, of convertingthe tin into the anhydrous liquid, it will be found most advantageous toproceed under conditions of temperature control. A single instance willserve to illustrate the general procedure: the preparation of C. P. oxidof tin from impure tin or hard head. Anhydrous chlorid is first preparedby introducing chlorin into anhydrous chlorid which contains the tinbearing material, preferably pulverulent. The mass of chlorid, afterbeing augmented fromthe metallic tin content of the hard head is thenfreed from foreign materials, as bysimple filtration and then distillingif necessary and later if chlorin is still found present, this issuitably removed as by agitation in the presence of pure tin or bydistillation or both. The purified anhydrous chlorid is then treatedwith distilled water by preferably adding the former to the latterto apoint of about twenty-five degrees-B. To

this solution, preferably while still hot, is 7 added a suitable alkali,for instance, milk of limein its pure state, until the whole mass isperfectly neutral or brought to the requisite conditions, whereupon theoxyhydrate of tin is precipitated and separated from the solution byfiltration, and perfectly dried, if this i is to be the final roduct;but if the ure oxid is required, ee from the combined water, thehydrated oxid is ignited'.or

furnaced appro riately, yielding a heavy white, highly pu verulentproduct of surpassing brilliancy.

The above instance serves to illustrate the importance of the purifyingstep of the process.

The process as a whole is thus seen to-serve at least two usefulpurposes, viz: the preparation of pure tin compounds from impuretin ortin-bearing material, thus effecting an important saving in the firstcost'of the tin and furthermore to produce a product from this source ofgreat intrinsic purity. It is of course to be understood that the stepsmay be varied to suit the special terminal product required, so long assuch steps fall properly within the scope of. the invention:

lie

pounds from tin bearing material, which con sists in treating the tinbearing material with aihalogen reagent, producing thereby a liquidanhydrous tin compound containing foreign substance, distilling theliquid, thus separating the anhydrous tin compound from the foreignsubstance and obtaining it practically ure While still in the anhydrousstate and.

adding a diluent to the distillate.

3 The process of preparing p re tin compounds from tin bearing materlalwhich consists in treating the .tin bearing material with a halogenreagent, producing thereby a liquid anhydrous tin compound containingforeign substance, distilling the liquid and thus separatingtheanhydrous tin compound from the foreign substance and obtaining itpractically 15 pure While still in the anhydrous state and adding wateras a diluent to the'distillate.

In testimony whereofl have hereunto set my hand in presence of twosubscribing witnesses.

- ELMER A. SPERRY.

Witnesses: ALFRED L. GRIFFITH A. R. GnBBs.

